The present invention relates generally to a multi-phase DC-to-DC converter, and more particularly, to an apparatus and method for balancing the channel currents in a multi-phase DC-to-DC converter.
The multi-phase DC-to-DC converter has been widely used for power supply circuits. Unfortunately, there may be current unbalance occurred between the channels thereof due to the mismatching of parameters and components between each of the phases or channels. A multi-phase DC-to-DC converter provided by U.S. Pat. No. 6,278,263 issued to Walters et al. can equally shares the load current between each of the phases or channels in the converter, by which all of the channel currents are sensed and averaged with summing circuit and scaling circuit for balance control between each of the channels. However, the circuit disclosed by this prior art is complicated due to the requirement of averaging operation of the channel currents and thus disadvantageous to integrate the converter circuit on a chip and to reduce the cost. If the averaging apparatus and method for the channel currents can be removed from a converter circuit, it will be scaled down. It is thus desired a simplified circuitry for current balance in a multi-phase DC-to-DC converter without averaging the channel currents. Moreover, it is another important issues of the method and circuit to sense each of the channel currents in the converter so as for further operation of the sensed signals each representative of a respective channel current for the control of current balance thereof. Based on the theory applied in the converter circuit of U.S. Pat. No. 6,278,263 as mentioned, it is necessary a current feedback resistor and its related circuitry to be inserted between each phase output and the control circuit of the multi-phase DC-to-DC converter to produce a current signal representative of the channel current on the respective phase or channel for the balance control thereof, which is also referred to U.S. Pat. No. 6,246,220 issued to Isham et al., for example. The current feedback resistor and its related circuitry induce additional cost and circuitry complexity and are preferred to be removed or simplified. It is therefore desired a multi-phase DC to DC converter with channel current balance based upon an alternative theory so as to simplify the feedback circuitry for sensing the channel currents thereof.
One object of the present invention is a simplified circuit for a multi-phase DC-to-DC converter with balanced channel currents.
Another object of the present invention is a method for balancing the channel currents in a multi-phase DC-to-DC converter.
Yet another object of the present invention is to simplify the feedback circuitry for sensing the channel currents in a multi-phase DC-to-DC converter.
In a multi-phase DC-to-DC converter with a converter output voltage and a plurality of channels each configured for generating a channel current, according to the present invention, the output voltage is sensed and compared with a reference signal to produce an error signal for each channel for a multi-input pulse width modulator or a multi-input comparator in conjunction with an ordinary pulse width modulator to produce a PWM signal to regulate the corresponding channel current. The multi-input pulse width modulator compares the error signal with a ramp signal and the corresponding channel current with each other of the channel currents to produce the corresponding PWM signal. Alternatively, the multi-input comparator subtracts the corresponding channel current from each other of the channel currents and sums the error signal to produce a combined signal for the ordinary pulse width modulator to compare with a ramp signal to the corresponding PWM signal.
In some embodiments, a current mirror or a pair of load devices connected with one or more input stages for the error signal, ramp signal and the other signals corresponding to each channel is provided for the PWM modulator. For some other embodiments, common gated transistors with a same bias are provided for the multi-input comparator.
For the comparisons between the channel currents, each of the channel currents is sensed to produce a feedback current sense signal in voltage type or current type. A current sense circuit to sense the channel current of each channel to produce a feedback voltage signal for the current balance control is also provided.